A.T. Robertson Commentary Acts 10:30

"And Cornelius said, Four days ago, until this hour, I was keeping the ninth hour of prayer in my house; and behold, a man stood before me in bright apparel," — Acts 10:30 (ASV)

Four days ago (απο τεταρτης ημερας). From the fourth day, reckoning backwards from this day.

I was keeping the ninth hour of prayer (ημην την ενατην προσευχομενος). Periphrastic middle imperfect and accusative of extension of time (all the ninth hour).